A Molecular Genetic and Physiological Comparison of the Hybrid Necrosis Response in Wheat (Triticum Aestivum L.) to Biotic and Abiotic Stress Responses

Expression of hybrid necrosis in plants can lead to a significant reduction in productivity, or even lethality. Epistatic interactions between divergent loci that have evolved through evolution are proposed as being responsible for the genetic incompatability that is expressed as hybrid necrosis. Hybrid necrosis can also represent an obstacle to the transfer of desirable traits from wild, related species to domesticated bread wheat. In wheat, expression of dominant complementary genes Ne1 and Ne2, located to chromosomes 5B and 2B in a hybrid results the production of necrotic leaf tissue, stunted plant growth, and reduced grain yield, which are similar plant responses to many biotic and abiotic stresses. This study was undertaken to compare the molecular genetic and physiological hybrid necrotic responses in wheat with those typically observed for biotic and abiotic stresses. Objectives were to; (1) measure levels of reactive oxygen species (ROS) and , xanthine dehydrogenase (XDH) during wheat hybrid necrosis, (2) assess the impact of temperature on the expression of hybrid necrosis, (3), assess the allelic interactions responsible for necrosis, and (4) characterize the genes upregulated during the expression of hybrid necrosis in wheat. The production of H2O2 in hybrid necrotic plants was not significantly different than in non-necrotic parents, suggesting that unlike some stress responses, elevated H2O2 levels are not responsible for causing programmed cell death and tissue necrosis in wheat. Reduced plant growth and yield in the allopurinol treated plants, and those plants expressing suppression of XDH affirms the role of XDH in purine catabolism and most likely nitrogen reassimilation in plants. Similar to the temperature sensitive expression of some disease resistance genes in wheat, expression of necrosis symptoms was reduced when hybrids were grown at 30OC. The SSR markers; Xbarc7, Xbarc13 and Xwmc344 are linked to the Ne2 gene at distances of 3 cM, 4 cM, and 6 cM, respectively, and Xgwm639 is linked at 11 cM with Ne1. There was an observed dosage effect associated with the Ne alleles, and both ‘Alsen’ and synthetic hexaploid wheat line ‘TA 4152 -37’ expressed moderate necrosis due to the Nem alleles. Gene expression analyses revealed that defense signaling genes were highly up-regulated during the expression of hybrid necrosis along with the activation of several antioxidant enzymes. Detection of high levels of polyamine oxidase activity during hybrid necrosis suggests that this enzyme could be the main source of ROS responsible for tissue cell death. Genes typically encoding for plant recognition receptors (PRRs), pathogenesis–related proteins, antioxidant enzymes, calcium regulation, protein kinases and ethylene biosynthesis were all up-regulated during expression of wheat hybrid necrosis. Results support the concept that hybrid necrotic symptoms in wheat are the byproduct of an autoimmune type of response similar to many responses invoked by wheat plants when exposed to a biotic, or abiotic stress

Dual Monte Carlo and Cluster Algorithms

We discuss the development of cluster algorithms from the viewpoint of probability theory and not from the usual viewpoint of a particular model. By using the perspective of probability theory, we detail the nature of a cluster algorithm, make explicit the assumptions embodied in all clusters of which we are aware, and define the construction of free cluster algorithms. We also illustrate these procedures by rederiving the Swendsen-Wang algorithm, presenting the details of the loop algorithm for a worldline simulation of a quantum $S=$ 1/2 model, and proposing a free cluster version of the Swendsen-Wang replica method for the random Ising model. How the principle of maximum entropy might be used to aid the construction of cluster algorithms is also discussed.Comment: 25 pages, 4 figures, to appear in Phys.Rev.

The electron pressure in the atmospheres of late-type dwarfs

Over-ionization of potassium and sodium in late-type dwarf star

Energy Audit in Wastewater Aeration System

To evaluate the energy consumption air to aeration basins in wastewater treatment aeration system and to compare the standard computations of oxygen demand and blower power requirements with the actual plant data

Cluster update and recognition

We present a fast and robust cluster update algorithm that is especially efficient in implementing the task of image segmentation using the method of superparamagnetic clustering. We apply it to a Potts model with spin interactions that are are defined by gray-scale differences within the image. Motivated by biological systems, we introduce the concept of neural inhibition to the Potts model realization of the segmentation problem. Including the inhibition term in the Hamiltonian results in enhanced contrast and thereby significantly improves segmentation quality. As a second benefit we can - after equilibration - directly identify the image segments as the clusters formed by the clustering algorithm. To construct a new spin configuration the algorithm performs the standard steps of (1) forming clusters and of (2) updating the spins in a cluster simultaneously. As opposed to standard algorithms, however, we share the interaction energy between the two steps. Thus the update probabilities are not independent of the interaction energies. As a consequence, we observe an acceleration of the relaxation by a factor of 10 compared to the Swendson and Wang procedure.Comment: 4 pages, 2 figure